The Pediatric Hematology/Oncology Fellowship Program at the University of Colorado Denver (UCD) and The Children's Hospital (TCH) has a distinguished history spanning over 35 years. Over the last 5 years, the Training Program has benefited significantly with the transition to the newly built Anschutz Medical Campus (AMC). The Pediatric Oncology laboratories relocated in the 2004-2005 academic year into expanded, state-of-the art research space on the AMC. In September 2007, TCH also relocated onto the AMC into a new 1.44 million square feet hospital that includes 294 beds and serves patients from seven states in the Rocky Mountain region. Thus, for the first time in the history of the program, Pediatric Oncology trainees are located on one medical campus which includes TCH, University of Colorado Hospital, UCD School of Medicine, and the Colorado Biosciences Park. The Pediatric Oncology Fellowship Program and faculty also grew significantly in size during this transition to the new campus and now consist of 25 Clinical Faculty with 4 new fellows entering the 3-year Fellowship Program annually. In parallel, the T32 Research Training Faculty has been expanded to 30 members, increasing the opportunities given to fellows to perform laboratory-based, translational or clinical research in pediatric oncology. The T32 Training Faculty represent a broad range of scientific disciplines including cell cycle control and signaling, transcriptional regulation and splicing, virology, and immunology. Training Faculty with specific expertise in clinical research and translational oncology, including identification of novel biologic targets for drug development, have also been added. The Training Program was initially funded in 2000 with this T32 grant, and the current submission is the second competitive renewal of this support. Because of the breadth of the clinical experience, the outstanding clinical reputation of the Children's Hospital, and the new research opportunities available, fellowship candidates since 1993 have consistently increased in quality and dedication to an academic career. Indeed, 13 of 15 graduates in the last 5 years of the Fellowship Program are now in academic faculty, and all graduates since 2007 have academic faculty positions. The minimal fellowship duration is three years. The first year is devoted almost exclusively to clinical training, while at least 80% of time during years 2 and 3 is devoted to research. Currently there are 12 fellows in the Program, all of whom have previously completed their Pediatric residencies, with 8 currently in research training beyond their first clinical fellowship year. This proposal seeks funding for those MD fellows who elect to pursue research related to Pediatric Oncology in the second and subsequent years of the fellowship, and select PhD post-doctoral fellows committed to a career in pediatric cancer research. Both history and recent developments thus mark this training program as one of the best in the nation.